Forestry management fights the spread of sudden oak death disease in Oregon and California

When sudden oak death was discovered in 2001 by forest pathologists in Curry County, local stakeholders, state regulators and land managers jumped quickly on the devastating disease. Now 20 years later, sudden oak death is still contained to the county’s borders, but it’s an ongoing battle.

Everett Hansen, a now-retired Oregon State University professor, helped spearhead the effort to contain the spread of the disease. The initial goal was eradication, but limiting the spread proved to be a more attainable goal.

“From day one, we invoked legal machinery to mandate the destruction of diseased trees,” Hansen said in an article published by Oregon State University (OSU). “Every time we found a diseased tree we cut it down as fast as we could. We were going full bore. So, we went through all these years without any published data to suggest what we were doing was working.”

A new study published in the journal Forest Pathology now has data to back up their efforts, highlighting the promising efforts of two-decades of action to manage and reduce the spread of sudden oak death.

Continued effort and investment will be critical. The pathogen that causes the disease may survive in soil for several years, and has the potential to spread throughout the range of tanoak, which includes Coos, Douglas, and Josephine counties.

“Although complete eradication of sudden oak death in Oregon’s forests is off the table, land managers and local stakeholders are continuing to work together to slow the spread of this disease across the landscape,” says Sarah Navarro, forest pathologist with the Oregon Department of Forestry in Salem.

However, the story isn’t the same in other areas where sudden oak death is present, and that serves as a warning to Oregon.

This year sudden oak death doubled in presence in Sonoma County, California, and cropped up in Del Norte County on the border with Oregon. Two infected trees were identified in Jedediah Smith Redwoods State Park. The appearance worries scientists because it could mark the beginning of a bridge that brings to California a European strain of the disease that attacks conifers, possibly including Douglas fir.

“It’s cause for serious concern,” said Richard Cobb, an assistant professor of forest health at Cal Poly San Luis Obispo, in the Press Democrat. “It points the sudden oak death story in a new direction.”

Cobb pointed to Oregon as an example on how to protect California’s recreational and commercial forest resources. The Oregon’s Department of Forestry requested $1 million last year to continue eradicating the European strain by cutting and burning infected trees and nearby vegetation. As a result the infestation has spread up to three times slower than in California.

Since the mid-1990s, sudden oak death has killed about 50 million trees from southwest Oregon to Big Sur and infected about 200 million trees in California, Cobb said. About a billion trees are at risk in Oregon and California, concentrated in Del Norte, Humboldt and Mendocino counties.

There is no cure, but a pesticide called Agri-Fos has been approved as a preventive treatment, while cutting down bay trees close to prized oaks is the main control strategy recommended to landowners, according to the Press Democrat article.

Despite its success, the war against the disease is not over in Oregon, where officials are asserting that $30 million worth of forest treatments over the next 20 years could offset the loss of 1,200 jobs by 2028 and $580 million in wages from 2020 to 2038.

Learn more​ about how you can help prevent the spread of SOD in Oregon’s forests, including how to recognize quarantine boundaries and how to avoid transporting plant material contaminated with the disease to other parts of the state.